<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">
    <input type="text" v-model="obj.words">
  </div>

  <script src="../vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        words: '',
        obj: {
          words: ''
        }
      },
      watch: {
        words(newValue, oldValue) {
          console.log('变化了', newValue, oldValue)
        },
        'obj.words'(newValue, oldValue) { //这个注意带 '' 
          console.log('变化了', newValue, oldValue)
        }

      }
    })
  </script>
</body>

</html>